The present application relates to a semiconductor structure and a method of forming the same. More particularly, the present application relates to a U-shape gate dielectric structure for use as a component of a functional gate structure which includes a vertical gate dielectric wall portion that has a wall thickness along a lateral direction that is greater than a vertical thickness, i.e., height, of a bottommost gate dielectric portion of the U-shaped gate dielectric structure.
Field effect transistors (FETs) containing functional gate structures are the basic building block of today's integrated circuits. Such functional gate structures include a gate dielectric material and a gate conductor. With scaling of the functional gate structure pitch, there is not enough room for the gate conductor of such devices. As such, functional gate structures containing a U-shaped gate dielectric have been developed. In such functional gate structures, the U-shaped gate dielectric has a wall thickness along the lateral direction that is the same as the vertical thickness of the horizontal gate dielectric portion of the U-shaped gate dielectric. Generally, the uniform thickness is a thin as possible so as to improve device performance. However, such U-shaped gate dielectrics provide extra capacitance to the device.
As such, there is a need to provide a semiconductor structure that has benefits of a U-shaped gate dielectric, without the unwanted capacitance increase that is associated with prior art U-shaped gate dielectrics.